Converting double garage to two storey extension

[lowster]

Hi, I've been searching high and low for info and more to the point costs of building in sips. The garage I am looking at converting only has single skin walls (70's build) I know these will probably have to be replaced in order to support a second storey. The garage is 7m x 6m so 42msq per level, I have been told that to rebuild with brick on the same foundations (should they be good enough) would be £1000 per sqm which would make it a non starter for me.
However, if I built in Sips would it be significantly cheaper? I can't find any prices per sqm for this method let alone a construction company local (Leicestershire) or national.
Has anyone built using this method? Any info would be gratefully received. Thanks.

 

[^woody^]

You can leave the walls up and build on them. Timber frame or insulation direct onto the back of the wall and span a steel beam at first floor level to make a cavity wall, or timber frame all the internal leaf.

Factory made panels will be more expensive than making them yourself. And the cost between timber and masonry for a small extension will be more or less the same if paying trades. If DIYing, then you'll need to work out your savings are depending on what you are doing yourself.

You'll need to expose and confirm that the foundations are OK in any case. And underpin or renew if necessary.

 

[lowster]

Thanks for the response Woody, That's good to hear that I can go straight off the existing wall (foundations permitting) my plan was to render the whole building so not bothered if the entire upper floor is wood frame as long as it's cheaper! One other question though the garage is approx 900mm from the main structure of the house (see pic) is there any way to span the gap so it becomes integral to the house?

 

[^woody^]

Yeah, just span it with a lintel/steel beam for masonry, or timber beam for a timber frame.

That's going to make a dominant two storey extension though, so check if planning will allow it.